Histamine release from mast cells and blood basophils is being studied as one of the immunological mechanisms involved in inflammation. Among the histamine releasing agents employed are IgE antibody, and the Ca++ ionophore A23187. The relationships between IgE antibody crosslinking, basophil desensitization and histamine release were analysed by kinetic studies. Cultured rat basophilic leukemia cells are used as a model for the studies of the IgE receptor and changes in phospholipid methylation during cell activation.